JPS6220182Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a root canal length measuring device that measures the root canal length by inserting a probe into the root canal of a tooth and detecting the impedance value according to the insertion depth. It is.

When it is necessary to know the root canal length when treating a tooth, one electrode is brought into contact with, for example, the oral mucosa, and the probe serving as the other electrode is inserted into the root canal of the tooth. It is well known that the root canal length is measured by detecting the impedance between the two electrodes, and a low frequency oscillator is generally used as the source of the measurement current flowing between the two electrodes. Conventionally, in this type of root canal length measurement device, 60 (50) Hz from the electric light line, that is, from the commercial power supply, was used.
In order to avoid the effects of noise, dry batteries are used as a power source, and while various dental diagnosis devices operate using electric light lines as a power source, the root canal length measuring device is the only one that uses dry batteries as an exception. The situation is getting worse. For this reason, when attempting to configure a system that processes data from various diagnostic devices all at once, problems such as power supply isolation and The problem of power consumption arises. Furthermore, even though the system is running on commercial power, having to exceptionally replace the dry cell battery is not a good thing from the perspective of overall system operation, and may cause malfunctions or forgetting to replace the dry cell battery due to voltage drop. There was also the problem of ease of use.

The present invention has been developed with the aim of providing a root canal length measuring device that can be operated without any problems using a commercial power source by focusing on these points. an oscillator that supplies a measurement current across a pair of electrodes, and a differential amplifier that amplifies a signal output obtained from the probe;
It is equipped with a bandpass filter and a detection section, the oscillation frequency of the oscillator is set sufficiently higher than the frequency of the commercial power supply, the output impedance is set low, and the signal output obtained from the probe has characteristics that match the oscillation frequency. It is characterized in that the signal is sent to the detection unit via a bandpass filter having a bandpass filter. In other words, in the present invention, since there is a large difference between the oscillation frequency of the oscillator that supplies the measurement current to the probe and the commercial frequency, even if commercial frequency noise is superimposed, it is processed separately from the original measurement signal. Furthermore, since the output impedance of the oscillator is low, it is difficult for commercial frequency noise signals to be superimposed due to induction, etc. Furthermore, it is possible to use a bandpass filter that has characteristics suitable for the oscillation frequency of the oscillator to superimpose commercial frequency noise signals. Since it is possible to cut out noise signals, it is possible to perform highly accurate measurements without being affected by commercial frequency noise signals while using a commercial power source as a power source, and it is possible to perform measurements with high precision without being affected by noise signals at commercial frequencies. A root canal length measuring device without any problems can be obtained.

Next, one embodiment of the present invention will be described based on the drawings. Figure 1 is a block diagram of the embodiment device, where 1 is a 60 Hz or 50 Hz commercial power source (light line power source), 2 is a power supply unit that exchanges AC of the commercial power source 1 to DC, and 3 is a low frequency unit for measuring current. An oscillator that oscillates an output; 4 is an output adjustment resistor connected to the output side of the oscillator 3; 5 is a probe; 6 is a grounding electrode; 7 is a resistor; the resistor 7, the probe 5, the grounding electrode 6 series circuits are connected in parallel to the output adjustment resistor 4. 8 is a differential amplifier that amplifies the signal output generated across the resistor 7; 9 is a bandpass filter; 10
is a detection section, and the detection section 10 is a rectifier circuit 1 that rectifies the signal output that has passed through the bandpass filter 9 and obtains a DC output of a magnitude corresponding to the magnitude of the signal.
1, and an indicator meter 12 which is operated by the output of the rectifier circuit 11. In this configuration, when the grounding electrode 6 is held in contact with the oral mucosa at a suitable location, the probe 5 is inserted into the root canal of the tooth, and a measurement current is passed through the human body, the root of the probe 5 is The current changes depending on the insertion depth into the tube, and the voltage generated across the resistor 7 changes, so this voltage is amplified by the differential amplifier 8 to ensure that the tip of the probe 5 reaches the root apex. is read by the meter 12, and the probe 5 at that time
The length of the root canal is determined by measuring the insertion length of the root canal.

Here, the oscillator 3 has a sufficiently high frequency ₀ (e.g. ₀
= 1000Hz), and the output impedance at point A on the output side is set to a sufficiently low value (for example, several tens of ohms). At point B of the probe 5, 60
(50) Hz noise occurs, and this noise assumes that the resistance of the human body is 10MΩ, and that the noise enters from AC 100V through the human body to point B. If resistor 7 is 5KΩ, the noise voltage is 100V/10MΩ.
×5KΩ=50mV, which is approximately the same level as the signal level to be measured (several mV to several tens of mV). This noise is superimposed on the original signal and amplified by the differential amplifier 8, but since the characteristics of the bandpass filter 9 are set to have a narrow passband centered around ₀ as shown in FIG. Noise with a frequency sufficiently lower than ₀ is attenuated by the bandpass filter 9, and only the original signal with a frequency of ₀ is sent to the detection unit 10, and the meter 12 has a highly accurate signal that is not affected by noise. You will receive instructions.

Although not shown in FIG. 1, the power supply section 2 is also used as a power supply for each circuit section other than the oscillator 3, such as the differential amplifier 8, and the detection section 10.
The output obtained can be used not only for instructions by the meter 12 but also for instructions by light, sound, etc., or as various other control signals.

FIG. 2 shows an example of a specific configuration of the oscillator 3, differential amplifier 8, bandpass filter 9, and rectifier circuit 11, and since each uses a conventionally well-known circuit configuration, detailed explanation is omitted. do.
In the figure, R ₁ to R ₁₄ are resistors, VR ₁ is variable resistor, C ₁ to C ₄
is a capacitor, D ₁ and D ₂ are diodes, OP ₁ to _{OP 6}
is an operational amplifier.

As described above, according to the present invention, by using a commercial power source such as a power line as a power source,
It is easy to incorporate this root canal length measurement device when consolidating various diagnostic devices into a large dental diagnostic system, and it also eliminates maintenance difficulties associated with battery replacement and voltage drop over time. You can solve any problems you may have. Even so, the commercial power The effect of this method is to avoid as much as possible the influence of noise, which was a problem when using the method, and to perform root canal length measurements with high precision.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention;
The figure is a specific wiring diagram of the same as the above, and FIG. 3 is a characteristic diagram of the bandpass filter in the same. Explanation of symbols 1...Commercial power supply (light line power supply), 2
...power supply section, 3...oscillator, 5...probe, 6...
...Ground side electrode, 9...Band pass filter, 10
……Detection unit.

Claims (1)

[Scope of utility model registration request] One of the pair of electrodes is brought into contact with the oral mucosa, etc., and the probe serving as the other electrode is inserted into the root canal of the tooth.The impedance value between the two electrodes is detected according to the insertion depth, and the root canal length is determined. The root canal length measuring device is configured to measure a root canal length, and includes a power supply unit that converts commercial current to direct current, an oscillator that supplies a measurement current across the pair of electrodes, and a signal detection unit that detects a signal obtained from the probe. A differential amplifier for amplification, a bandpass filter, and a detection section are provided, the oscillation frequency of the oscillator is set sufficiently higher than the frequency of the commercial power supply, the output impedance of the oscillator is set low, and the bandpass filter is detected. 1. A root canal length measuring device, characterized in that the device is configured to have a characteristic of adapting a signal output obtained from a needle to an oscillation frequency.